Behind closed doors: use of visual cover by courting male three-spined stickleback, Gasterosteus aculeatus

Species that form breeding aggregations, such as the three-spined stickleback, have ample opportunity to observe and interact with others in their respective populations. This exposes courting pairs to distraction or disruption from onlooking individuals. Thus, courting inconspicuously could be beneficial to males. We tested whether males would court inconspicuously by housing them in individual tanks with visual access to a neighbouring male. A dummy of a gravid female three-spined stickleback was presented to a male in the front quadrant of the tank while screens concealed either the front quarter or front half of the tank from the neighbour. When a portion of the tank was concealed from a neighbouring rival, males courted more in the concealed areas than those that were exposed to a rival. Hence, in the presence of rivals, males can adjust their courtship behaviour in ways that could increase their mating success. Whether this reflects an active ‘strategy’ or a passive result of the male being less distracted by its neighbour is presently unknown.